The invention is directed to a catalyst for the production of hydrocarbons having a higher ethane selectivity from synthesis gas (a mixture of carbon monoxide and hydrogen).
An important chemical raw material for the chemical industry is ethylene, which is produced to a great extent by cracking petroleum derivatives. In view of the expense and scarcity of petroleum products, it is also known to convert synthesis gas to a hydrocarbon mixture having the highest possible content of ethane, which then is further processed to ethylene (see Chang U.S. Pat. No. 4,096,163. The entire disclosure of Chang is hereby incorporated by reference and relied upon including the U.S. patents mentioned therein).
The industrially desired product is ethylene. This is obtained from paraffin hydrocarbons having at least two carbon atoms by cracking, whereby the highest yield is obtained from ethane. For this reason, it is desired to carry out the transfer of synthesis gas into hydrocarbons in such manner that there is obtained the highest possible content of ethane in the product gas mixture. In view of the very large amounts which are reacted in industrial plants, a slight improvement of the selectivity or the space-time-yields already represents a significant industrial advance.
It is known to produce aliphatic hydrocarbons from synthesis gas (see Chang U.S. Pat. No. 4,096,163, col. 13, example 7). The catalyst employed thereby is a zinc exchanged ZSM-5/aluminum oxide-extrudate. The hydrocarbon gas mixture obtained contained in addition to methane, isobutane, and isopentane (36.4% ethane and 11.9% propane).
Since the yield of ethane of the known process does not have the desired selectivity, there is a need to develop a corresponding catalyst.